/*
 * $Header: /home/cvsroot/cvs/Reporter/JavaSource/jaoso/framework/web/filter/EncodingFilter.java,v 1.1 2006/02/15 10:23:39 zhangqi Exp $
 * $Revision: 1.1 $
 * $Date: 2006/02/15 10:23:39 $
 *
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Tomcat", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Role.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * [Additional notices, if required by prior licensing conditions]
 *
 */
package jaoso.framework.web.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * <p>
 * Example filter that sets the character encoding to be used in parsing the
 * incoming request, either unconditionally or only if the client did not
 * specify a character encoding. Configuration of this filter is based on the
 * following initialization parameters:
 * </p>
 * 
 * <ul>
 * <li><strong>encoding </strong>- The character encoding to be configured for
 * this request, either conditionally or unconditionally based on the
 * <code>ignore</code> initialization parameter. This parameter is required,
 * so there is no default.</li>
 * <li><strong>ignore </strong>- If set to "true", any character encoding
 * specified by the client is ignored, and the value returned by the
 * <code>selectEncoding()</code> method is set. If set to "false,
 * <code>selectEncoding()</code> is called <strong>only </strong> if the
 * client has not already specified an encoding. By default, this parameter is
 * set to "true".</li>
 * </ul>
 * 
 * <p>
 * Although this filter can be used unchanged, it is also easy to subclass it
 * and make the <code>selectEncoding()</code> method more intelligent about
 * what encoding to choose, based on characteristics of the incoming request
 * (such as the values of the <code>Accept-Language</code> and
 * <code>User-Agent</code> headers, or a value stashed in the current user's
 * session.
 * </p>
 * 
 * @author Craig McClanahan
 * @version $Revision: 1.1 $ $Date: 2006/02/15 10:23:39 $
 */
public class EncodingFilter implements Filter
{
    /**
     * The filter configuration object we are associated with. If this value is
     * null, this filter instance is not currently configured.
     */
    private FilterConfig filterConfig = null;

    // ----------------------------------------------------- Instance Variables

    /**
     * The default character encoding to set for requests that pass through this
     * filter.
     */
    private String encoding = null;

    /** Should a character encoding specified by the client be ignored? */
    private boolean ignore = true;

    // --------------------------------------------------------- Public Methods

    /**
     * Take this filter out of service.
     */
    public final void destroy()
    {
        this.encoding = null;
        this.filterConfig = null;
    }

    /**
     * Select and set (if specified) the character encoding to be used to
     * interpret request parameters for this request.
     * 
     * @param request
     *            The servlet request we are processing
     * @param response
     *            The servlet response we are creating
     * @param chain
     *            The filter chain we are processing
     * 
     * @exception IOException
     *                if an input/output error occurs
     * @exception ServletException
     *                if a servlet error occurs
     */
    public final void doFilter(final ServletRequest request,
            final ServletResponse response, final FilterChain chain)
            throws IOException, ServletException
    {
        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null))
        {
            String encoding1 = selectEncoding(request);

            if (encoding1 != null)
            {
                request.setCharacterEncoding(encoding1);
            }
        }

        // Pass control on to the next filter
        chain.doFilter(request, response);
    }

    /**
     * Place this filter into service.
     * 
     * @param arg0
     *            The filter configuration object
     * @exception ServletException
     *                error
     */
    public final void init(final FilterConfig arg0) throws ServletException
    {
        this.filterConfig = arg0;
        this.encoding = filterConfig.getInitParameter("encoding");

        String value = filterConfig.getInitParameter("ignore");

        if (value == null)
        {
            this.ignore = true;
        } else if (value.equalsIgnoreCase("true"))
        {
            this.ignore = true;
        } else if (value.equalsIgnoreCase("yes"))
        {
            this.ignore = true;
        } else
        {
            this.ignore = false;
        }
    }

    // ------------------------------------------------------ Protected Methods

    /**
     * Select an appropriate character encoding to be used, based on the
     * characteristics of the current request and/or filter initialization
     * parameters. If no character encoding should be set, return
     * <code>null</code>.
     * 
     * <p>
     * The default implementation unconditionally returns the value configured
     * by the <strong>encoding </strong> initialization parameter for this
     * filter.
     * </p>
     * 
     * @param request
     *            The servlet request we are processing
     * @return string
     */
    protected final String selectEncoding(final ServletRequest request)
    {
        return (this.encoding);
    }
}